1. Field of the Invention
The present invention relates to personal display systems, and more particularly, to a wearable display system capable of transmitting a display signal through an eyeglass-type or goggle-type optical device to be displayed at a location near an eye of a user.
2. Description of the Related Art
Conventional optical display systems used in the military, in medicine or for personal entertainment have been designed for users to see video signals via an eyeglass-type, goggle-type or helmet-type wearable device. These personal display systems allow the users to receive video information while moving from place to place. FIG. 1 shows one example of a conventional HMD. Referring to FIG. 1, the HMD is made of eyeglasses 100 and an image-driving unit 200 that is attached to the center of the eyeglasses 100. The driving unit 200 is bulky, heavy and unpleasant in appearance. The large volume and heavy weight of the image-driving unit 200 is due to the many optical elements constituting the unit.
FIG. 2 is a block diagram illustrating the structure of a conventional HMD. In FIG. 2, the HMD comprises the image driving unit 200, a display panel 210 and an optical system 220. The image driving unit 200 stores a signal received from exterior sources such as a personal computer or a video device (not shown) and processes the received signal to display it on the display panel 210, such as a liquid crystal display (LCD) panel. The optical system 220 generates a virtual image in the eye of a user from the signal displayed on the display panel 210. This is done via an image-enlarging optical system. The HMD can further include other head-mounted devices or a cable for receiving signals from an external source.
FIG. 3 shows the general structure of the optical system 220 of the conventional HMD of FIG. 2. The conventional optical system 220 is composed of a collimating lens 300, an X prism 310, focusing lenses 320, fold mirrors 330 and ocular lenses (or magnifying lenses) 340. The collimating lens 300 collimates the light (a signal) emitted from the display panel 210 or the like. The X prism 310 redirects light received from the collimating lens 300 in the right and left directions. The focusing lenses 320 are separately placed on the right and left sides of the X prism 310 to focus collimated light redirected by the X prism 310. The fold mirrors 330 reflect the light focused by the focusing lenses 320 toward the eyes of the user. The ocular lenses (or magnifying lenses) 340 allow small signals passing through the above-described optical elements to appear as a virtual image in the eyes of the user. At this time, if the light propagating through the optical system 220 is polychromatic, lenses for removing chromatic aberration must be used as the ocular lenses 340.
In the conventional HMD wearable display system, the optical system 220 employs several precisely designed optical elements, such as the collimating lens, the X prism, the focusing lenses, the fold mirrors, the ocular lenses, and the like, as described above. For this reason, it is difficult to manufacture the conventional HMD wearable display system because much effort and time are required. Even if the lenses and the other elements are designed precisely, additional difficulties in aligning the lenses and the other elements may occur. Moreover, a special eyepiece must be additionally designed to remove chromatic aberration of a color signal. Therefore, the conventional HMD wearable display system is expensive to manufacture. In addition, the conventional optical system 220 is bulky and heavy, therefore making the system uncomfortable for the user.